Control instrument



I l A. CALBWELL CONTROL INSTRUMENT Fu a Aug. a; 1938 4 Shelas-Sheeft. 1

IN V EN TOR.

JOHN A. CALDWELL BY ATTORNEY Filed Aug. 3, 1938 4 Sheets-Sheet 2 FIG. 3.

INVENTOR.

JOHN A. CALDWELL W ATTORNEY I 26, 1941- J. A. CALDWELL- CONTROL INSTRUMENT Fild Aug. 5, 1938 4 Sheets-Sheet 5 FIG. 4.

FIG. 5.

l" id" L & Y T E NL N E R V m mA m N H O J Aug. 26, 1941- J. AQCALDWELL comm. INSTRUMENT Filed Au :5, 1938 4 Sheets-Shget 4 INVENTOR.

JOHN A. CALDWELL NEY Patented Aug. 26, 19 41 UNITED .STATES PATENT orrlcs- CONTROL INSTRUMENT John A. Caldwell, Philadelphia, Pa., assignor to The Brown Instrument Company, Philadelphia, Pa., a corporation of Pennsylvania Application August 3, 1938, Serial No. 222,823 I 22 Claims. (01.200-56) a part of this speciflcatlonr For a better un- The general object of the present invention is to provide a means to control the energization of a motor in accordance with variations in some which the device is capable of operating, or a control in which a change in the value of the steam pressure is used to produce a proportional change in the opening of the damper or fuel valve. y

In the form of my invention which is described below, I .use a member which is responsive to steam pressure to adjust the path of movement of another member; The second member is periodically moved through one of a plurality of paths to energize a motor in one direction or the other to open or close a fuel supply valve to a heater for a boiler that generates the steam, in order to keep the steam pressure within desired limits.

Themechanism through which the two abovementioned members produce the desired control effects may be of various forms. Advantageously, however, that mechanism includes two mercury switches, one for energizing the valve which are selectively moved according to the path the second member is following. A third switch in series with both of the other switches, or in a common motor line, is, periodically opened and closed to regulate thetime that the motor is energized in each operation and, therefore, the increment of movement of the valve for each changein pressure of the steam.

Although -I describe the use of my invention as being responsive to steam pressure, it isobvious that the device could be responsive to any change in pressure, such as draft pressure in a furnace or water pressure. In fact, the instrument may be used to control any condition which can be made to produce a change in dimension of some measuring element. h

The various features of novelty which characterize my inveniton are pointed out with particularity in the claims annexed to and forming .derstandlng of the invention, however, its advantages and specific objects obtained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention. r

Of the drawings:

Fig. 1 is a front view of my control instrument; Fig. 2 is a sectional view taken on line 2--2 of Fig. 1;

Fig. 3 is a view of my device taken on line 33 of Fig. 4; v

Fig. 4 is a view looking from theright of Figs. Land 3 with the Bourdon tube broken away for the sake of cleamess;

Fig. 5 is a wiring diagram; Fig. 6 is a modified form of follow-up to be used in place of the one shown in Fig. 3; Fig. 7 is a viewof the feeler mechanism; Fig. 8 is a view taken on line 8--8 of Fig. 7

Flg. 9 is a view of the cams'and the parts 0perated thereby, and

Fig. 10 is another view of the follow-up mech-- anism of Fig. 3.

The mechanism of my device is mounted on a plate I that is in turn attached to a supportv 2 of any suitable shape that may be mounted in some convenient location.- A casing 4, taking the form of a box-like cover, is attached to the support 2 by studs 3 and serves'to protect the mechanism of the instrument from dust and undesirable fumes. In furtherance of this object,

a gasket 5 of rubber, or other material, is provided between the cover land support 2.

A Support for a pressure responsive element ll consists of another and smaller plate I that is fastened to plate I. terminal block I, for leads from the various mercury switches that are used, and a pin I upon which is pivoted a freelyswinging pointer 9 that,- in cooperation with a mark on the plate i, is used to indicate when the instrument is level.

There is provided on plate 6, a support It for the pressure responsive element taking the form of a Bourdon tube II that is responsive to the pressure being measured, which, in this case, is

illustrated as being steam pressure in a boiler ii to which it is connected by a tube l2. As the pressure in the boiler II is varied, changes in the size of the Bourdon tube II are used to control the fuel going to burner ll through supply pipe I! by varying the opening of valve It. In order to accomplish this, there is provided 'a re- The plate 6 also supports a versible motor II which, through suitable gearing, changes the opening of valve II in response to changes in steam pressure in a manner now to be described. It should be understood that if the Bourdon tube was, for example, responsive to changes in furnace pressure. the motor I! could be used as a damper motor to vary the opening of a suitable damper;

Variations in size of the Bourdon tube II are transmitted to a pointer member which in turn controls the movement of a switch actuating member for the circuits of motor. H. The connections between the Bourdon tube and the pointer are shown best in Fig. 1 and consist of a link I! pivoted at one end to the tube H and having a slot ii in its other end. A screw 20, having a groove in its head to be received in slot It, has a clamping nut ii on its other end so that the screw can be adjustably receivedat any point along the length of slot 22 inlever member 23 which is pivoted at 14 on a support 28 attached to support 8. By adjusting screw 20 I along slot 22, the differential or responsive range of the device can be adjustedi In,other,words, it screw 20 is adjusted to the left in Fig. 1, the lever 23 will be moved through 'a smaller arc for a given change in sizeof the Bourdon tube due to a given change in the pressure to which it is responsive than it would be moved it the screw 20 is adjusted to the right, nearer pivot 24. Provision is made for adjusting the position of lever lengthwise of link II for setting the apparatus correctly at its neutral position. Such an adjustment consists of screw 25 that threads through a bent-over portion on the lower end of link It, see Fig. 2, and bears against the lower side of nut 2|. There is also provided a lock nut 24 for screw 25 and a pointer 21 on link ll coopcrating with a scale on the lower edge of link I! .to indicate the diflerential setting being used.

A segment I! for transferring the movement of lever '25 to the pointer is also pivotally mounted at 24 and is held by spring against inturned edge II oflever, 23. This connection iorms what may be termed an overload release, since i! the Bourdon tube II is subjected to excessive pressure, the lever 23 can move independently of the, segment 2! against the bias of spring 30. The teeth of the segment 25 are in mesh with a pinion II on a shaft 54 thathas attached to its other end, between plates I and I, the above-mentioned pointer 34. The pinion l2 and pointer 54 are biased in a clockwise direction by a pair of hair springs 15 in order to prevent anyback lash in the gearing and thus make the instrument more sensitive. In order to provide various control steps on the pointer 84. a plate 34 is attached thereto in such a manner thatits lower edge projects below that of I pointer 34 and provides, with the pointer, edges II and a. A third control position is provided when the pointer is moved to the left to such an extent that both edges 81 and II are out of the path of movement of a feeler, now to be described.

A feeler II that is .provided with an engaging edge 40 and a guide 4|, is pivotally mounted a,ass,eas

arm extending in a generally horizontal direction that is received between rollers 45 on the feeler 54. The other arm of bell-crank 44 is fastened to a second bell-crank 41, and the two are biased in a counter-clockwise direction around pivot 45 by a spring 45 into a position limited by contact between edge 40 and one of the edges 31 .or 38, or by engagement between the upper arm 41a of bell-crank 41 and a stop pin 49.

The bell-cranks 44 and 41 are periodically moved clockwise against the bias of spring 48 in order to free the pointer 34 so that it may take a new position. This movement is accomplished by a roller 50, supported between two cams 5i and 52, that, upon rotation of the cams in a counter-clockwise direction, engages the top edge of the lower arm of bell-crank 41. These cams II and 52 are mounted on shaft 53 and are rotated at a constant speed by motor 54 through gearing 55 which is received in a recess in support 2 back of plate I.

The ultimate position of feeler 39 on its upward excursion is used to position a switch actuating member. This member is then moved through a path to close one or the other of, or neither of, a pair of control switches, depending upon the then value of the pressure in boiler II. If one of the control switches is closed, the

actuating member also gives a follow-up movement to the feeler 39 so that the instrument will then control at 'a different pressure within its adjusted range.

The above-mentioned switch actuating member consists of a triangular plate 56, provided in its side edges with slots 51 and 58, that is pivoted at its lower end to a stud shaft 59 which is supported by a link Bil movable around stud shaft 45. The stud shaft 59 is provided with a roller 5i that rests on the surface of cam- 5|. Positioning of the actuating member 56 is accomplished by a link 82 that is fastened at one end to the center of member 56 and at its other end to the upper arm 41a of bell-crank 41. It is noted that link 82 extends parallel to link 45, for a purpose to be later described.

From the above described arrangement of parts, it can readily be seen,that as the pressure in boiler I8 varies, the position of pointer 34 will vary. Thus if the boiler pressure is at its desired value; pointer 34 will be in such a position that, upon its upward stroke, edge 40 of feeler II will engage edge 38. The movement of bellcranks 44 and 41 will then be stopped at a time when bell-crank 41, through link 52, has moved actuating member 5! to a vertical position. If the pressure in boiler I3 is high, the pointer 34 will be moved counter-clockwise, and edge 45 will i on its--up-stroke engage edge 51. Since bell-crank '41 does not move counter-clockwise so much as when the pressure is at its desired value, the link I! will hold actuating member 55 in a position tilted .to the right of the vertical. In a similar manner, it the pressure is low, edge 44 on its up-stroke will pass to the right of edge II, and movement of the bell-cranks will be stopped by engagement 0! arm 41:: with stop pin 45. Thus, link I! will pull member 5| to a position to .the left of vertical.

when actuating member 54 is moved to the right of vertical due, to high pressure, its slot 5. will encircle a pin 58 on a pivoted mercury switch support 44. This support 44 is pivoted at O5 and biased in a counter-clockwise direction by a spring a against a stop 44a. Adjustably mounted on the support 44 is a bracket 41 that supports a mercury switch 09 which is in circuit with one of the fields of reversible motor i1. When the actuating member I9 is tilted to .the left of -vertical due to low pressure, its slot '51 encircles a pin 68 on one end of a switch support 10 that is pivoted at H and biased in a clockwise direction by a spring 12 against a stop 12a. Adjustably fastened to the support 19 is a bracket 13 for mercury switch I! that is in circuit with the other field of motor I'I.

Just after roller '50 has run off the upper edge of bell-crank ll, which on its tip-stroke has In order to insure the energization of motor i! in either one direction or the other for a predetermined time each cycle, there is provided a switch 8| in the commoniine to motor llwhich breaks the circuit thereto a predetermined time after either switch 99- or switch "II has been closed. This switch II is mounted in bracket 9! that is adjustably fastened to support 93, which is in turn adjustably fastened to a lever 04. Lever 94 is biased in a counter-clockwise direction around its pivot 95 by a spring 99 so that a roller 91 on its outer end is riding on the surface of cam 52. Inasmuch as cam 92 is in fixed relation to cam Ii, which raises member 90 to close 5! is encircling pin 89, .it will remain at that inclination for its entire movement. If there was a change in the pressure in boiler II from that of the previous cycle of the instrument, the actuating plate 56 will be tilted, and just prior to the end .of its up-stroke, a follow-up movement will'be given to the feeler 39 by a means new to be described.

The support 4: for the feeler as is attached to a sleeve 14 (see Fig. 4) rotatable on a shaft 15 mounted on plate i. sleeve 14 is a cross-piece 16 that has ratchet teeth ll formed in each end. The construction is such that as the cross-piece i6 is moved, the

, sleeve 1'4 and support will also be moved around ment between one .end of spring 92 and an ec-v centric pin 83 mounted on lever 8|.

In a like manner, the pawl 19 is pivotally mounted at 84 on one end of a lever member 95, also mounted on shaft 75, that is biased clockwise by the engagement between the other end of spring 92 and an eccentric pin 96. Downward movement of the pawls-TB and I9 and their supporting levers is adjustably limited by engagement between them and eccentric pins 81 and 89 respectively.

From the above, it will be seen that the followup movement of feeler 99 is obtained in the following man;;er. Just prior to the time member 56 reaches the upper limit of its movement, its upper edge 58A, if member 56 has been tilted to the left, will engage eccentric pin 89 and start moving lever 8| and its pawl II in a clockwise direction. As this occurs, pawl 18 will also turn clockwise around its pivot 89 on lever 9i to bring its edge 89 into engagement with one 0f-the teeth 11 and thus move cross-member l9 to-shift feeler 39 to the left. The amount of movement of cross-piece 19 will be. the distance of one tooth 11. In a similar manner, if member Attachedto the rear of the switch 99 or switch 14, the lever 94 will be moved in timed relation thereto to .operf switch II a,

given length of time after switches N or 14 have been closed. Thus, motor I! is energized for equal increments of time for 'eachcycle of the instrument.

In the operation of the instrument, the pointer 34 is positioned by the Bourdon tube I i in accordance with the value of the steam pressure in boiler ll. Thereafter as roller 59 moves along the edge of the lower arm of bell-crank 41, that member along with bell-crank M will rise under the bias of spring 49 until the edge 49 engages either edge 31 or edge 38, or passes to the right of pointer 39. If, for example, the steam pressure is low,

I length of time in the same direction the edge will pass to the right of pointer 94, and link 92 will move actuating member 59 to the left of the vertical so that slot I1 encircles pin 99 on mercury switch support It.

At this time, the Cam it will start to raise roller GI and actuating member 56 so that switch 14 will be closed. Motor I! will then be run in a direction to open valve l6 and supply more fuel to the burner H. The motor "will continue to rotate until cam 50 has tilted bracket 9| enough to open switch 9| and break the motor circuit. Thus, the motor has opened the valve I ,L 4 a given amount, and if the steam pressure is 'still undesirably low upon the next cycle of the instrument, the motor I! will be run for the same to open the valve further.

Just prior to the time actuating member 99 reaches the top of its stroke, its edge "A will engage the pin on lever 8| to bringv edge 09 of pawl 19 into engagement with one of the teeth 11. Continued movement of member 56 will then move lever 16 clockwise so that arm 43 attached thereto will shift feeler 39 and edge 49 to the left.

- This in effect. gives a follow-up movement to edge 40 and, at the same time, permits the instrument to control at a lower pressure.

If the drop in pressure is a predetermined amount governed'by the adjustment of pin ll, the next time edge 40 rises it will, due to its shifting to the left, engage edge '38, and no further control action will be made. The amount that feeler 39 can be shifted to the right or left determines the limits of the rangethrough which the pressure of the boiler i3 is permitted to vary. Be-

58 is tilted to the right, on its upward movement.

II to raise or lower the pawl carrying membersll and 85 and thereby vary the amount they will be moved by edge "A of member ll.

tween these limits, the valve I. will be given a small adjustment, and due to the follow-up of feeler 39, the instrument will energize the motor i1 in a manner calculated to make the valve position correspond to the existing pressure value. This proportionalaction will take-place within the range determined by the range of action of part 19, and beyond that range in either.

direction the motor will be energized in each cycle of the instrument to open the valve l9 and supply more fuel to burner it until the steam pressure has returned to some value within its normal range.

It the pressure has increased, edge It will engage edge 31 of ieeler 84 to move actuating member it to the right and close switch ll. This cycle of the instrument will also give a follow-up movement or ieeler 3D to the right to reverse the above described operation. I

A modified form of mechanism to procure the follow-up movement of feeler- I! is shown in Fig. 6. In the follow-up mechanism shown in Fig. 3, a pawl and ratchet mechanism was used, and the amount of follow-up was determined by the setting of eccentric screws 81 and II. The followup Fig. 6 diners therefrom in that there is disclosed in that figure a friction type follow-up which is disengaged alter a predetermined movement of member 16 and the ieeler II.

A tubularsleeve III, serving the same purpose as shatt'll oi. Fig 4, is extended forward from the supporting plate i or the instrument. Rotatable on this sleeve is. the member I'll that caradjushnentoi'pinsll auditor llland Ilirelative to each other.

While in accordance with'the provisions of the statutes, I have illustrated and described the best form of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set iorth inthe appended claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire ,to secure by Letters Patent is:

1. In an instrument to control the value of a condition between normal limits, a first member positioned in accordance with the value oi. said condition, a periodically moved member, means to move said second member through a path wherein it will engage said first member or not,

depending upon the value of the condition, a part rice the support it to which the Ieeler I. is attached. Also rotatably mounted on. sleeve III is a pawl supporting member I that is provided with a backwardly'extending lug Ill. The member I is normally held in a horizontal position by a coil spring Ill encircling sleeve ill, the upstanding ends of which are crossed, as indicated at Ill, and=engage the lug IO! and a pin Ill extending from plate I. In this manner, any tilting movement of the member I is opposed by one of the ends of the spring ll. Pivotally mounted at I" on the right end of member III is a pawl III which has a lug Ill extending through opening ill that is adapted'to be engased by the edge "A of actuating member It and a clutch edge- III which is adapted to engage the edge 8 of member I'll. In a like manner. a pawl III is pivoted on member Ill at III and base lug Ill extending through opening llt anda clutchedge lll adapted'to engage edge ill or member "I.

positioned in accordance with the position 0! said second member, means to move said part, and means moved by said part to adjust said second member in a direction-to oil-set the effect of movement of said first member.

2. In a control instrument, a first member having an edge with a step therein movable in accordance with variations in'a measurable condition, a second periodically moving member adapted to engage said edge, said step, or to pass beyond said step depending upon the value oi! said condition and therefore the position of said Downward movement or the pawls m and m' islhnitedbytheengagementottheirinnerends with a collar II! on sleeve Ill, and inward movement of the inner ends ofthe pawls is first member, a part positioned by said second member, means to move said part through a path depending upon its position, and means engaged by said part during its movement to shiit said second member towar'd a position where it will en age said step. 3

8. In a control instrument, a part having slots in it, a first and a second tiltable lever, each lever having a projection on one end and each pro-e iection being adapted to befencircled by one oi said slots, means topositlon said part in accordq ance with the value of a condition, the position limited byeccentricpins III and I2! respectively.

In the operation oi this embodiment, it member II is in a vertical position. indicatingnomial pressure. it will passbetween lugs iii and ill on its lip-stroke, and no movement of member IIO will occur. Ii, however, member I is tilted. for example. to the sight, it will first cloaeswltch a. andtheieai'teredge ssswmeneueh'um. to raise'the lug. Upon c mment of lag Ill, thepawl lliwillmovearounditspivottollrihg its edge H2 into engagement with edge ill at number n. to m m m so )Ithee'onditionisaboveits normal value, thepart It to the right. This movement oontl'mes until theupperedgeoi' pawl ill pin "I. at which time continued mov'unmt oi thepawlwillmvotitas-oundthepin II. andmoveedge lllouto! enoasementwithedge m.

'lhusmemberlll ismovedirom thetimeedge illengagesedge lliuntilthe pawl Ill engages pin l2l, whichmovementeanbe.vadedbyadimflngtheeccentrlcsln. Ina similar manner, tlse'member lllwlllbemovedmtheopposite oireeuenueoeesssensaseslusus rpawi Ill. I

In either embodiment of the invention tbe follow-up movement on be made difiesent for c! said part being such that ii the condition is above a normal value, one slot will encircle one projection, and it the condition is below normal,

the other slot will encircle the other projection, means to move said part whereby the corresponding lever-will be tilted; and means responsive to the tilting of said lever to adjust the condition toward normal.

4. In a control instrument, the combination with a pair of tiltable'levers, a part adapted to individually move said levers, means to position mid part in accordance with the value "of a condition, the position of said part being such that willbelnpositiontotilt one lever,andiithe oonditionisbelownormahthepartwillbein position to tilt the other lever. means to move said part through a pathdepending p n its as position to thereby tiltone or the other of said -levers, means responsive to the tilting-oi said lever to adjust said condition toward normal, a

third lever. means to-mov'e said third lever inv 'lynchronismwithsaidpattmndmeansrespon rungeua nng mbrmereochu'mne the 1s aivetomovementotsaidthirdlevertolimitthe adiustmentoiiheconditionbysaidfirst'levers.

5. In a controlimtrument, the combination with a member adjustable in accordance with the value of a condition to be controlled, said memberbeingprovidedwithan'edgehavinga 'movement of said member.

8,858,088: step in it, 'a periodicallymovable adapted to engage said step if the condition is at a normal value, and adapted to engage said edge if the condition is to oneside of normal, and to pass beyond said step it the condition is to the other side of normal, means to move said periodically movable member from a predetermined first position to a second position depending upon its engagement with said first,member, a part positioned in accordance with the second position of said periodically movable member, means to move said part through a path, and means engaged by said part to-shift said periodically movable member in a direction so that it will engage the step of said first member.

6. In a control instrument, the combination with a member positioned in accordance with .the value of a measurable condition, said memher being provided with an edge, a second member adapted to engage said edge or pass beyond.

it and being shiitable in a direction parallel to 11. The combination with a deflecting meter element, a pair of opposed electrical contact devices pivoted on individual substantially parallel axes, a part, an actuating member mounted on said part for oscillatory movement about a third axis parallel to the first-mentioned axes, means cooperating with said element and member to adjust the latter about said axis in accordance with the position of said element, means to give said part to-and-fro movements to oscillate said number over paths determined by the member adjusting means, said devices having portions adapted to be engaged by said member selectivesaid edge, means to move said second member irom a first predetermined position to' a second position depending upon whether it eng ges said edge or not, a pant positioned by said second member, means to move said part through a path depending upon its position, clutch means adapted to be engaged by said part as it moves, a lever connected to said second member and moved by said clutch means whereby said second member will be shifted along said edge upon movement of the part.

'7. In a control instrument, the combination with a first member positioned in accordance with the value of a measurable condition, a

\ second shiftablemember, means .to periodically move said second member into engagement with the first, a part positioned by said second member, means to move said part through a path, a lever connected to said second member, a pair of clutch members adapted to engage and move said lever, means to move said part into engagement with one of said clutch members depending upon its position to move said lever and shift said second member whereby the second member will engage said first member at a difierent point.

8. In a control instrument, the combination with a pivoted lever having teeth on each end,

, a pair of arms pivoted coaxially with said lever,' an over-weighted clutch member on the free end 01 each arm, each clutch member adapted to engage one set of teeth to move said lever, a part, means to move said part through a predeter- 'mined path to engage one or the other of said clutch members, whereby said clutch member will move said lever, and means actuated by movement of said lever.

9. In a control instrument, the combination with a pivoted lever, an arm pivoted coaxial with said lever, a clutch member adapted to engage said lever mounted on each end of said arm, a

- part, means to move said part through a path to engage a clutch member whereby saidclutch member will engage and move said lever, means to disengage said clutch, and means actuated 10. In a control instrument, the combination with a measuring element and a control mechanism of means connecting said element and mechanism comprising a segment, a lever resiliently movable with respect to said segment, and means connecting said lever and element,

the last-named meansbeing adjustablein a plurality of planes.

the path oi! travel of said member adjusting means includes means for ad- Justing said member independently of said element in responsetoa movement of said member;

13. The combination of a mercury switch bracket mounted for rotation about an axis and having an actuating portion, a second mercury switch bracket mounted for rotation about a second axis and having an actuating portion, a member oscillated by power means over paths selectively determined by meansresponsive to a variable condition and adapted to selectively engage said actuating portions in accordance with its path oi. travel, and means responsive to the oscillation of said member to change the path of travel of said member.

14. Reversible motor control means including a pair of switches, an oscillatory member adapted to selectively operate one of said switches when constrained for movement along one path, to selectively operate the otherof said switches when constrained for movement along a second path,

insaid condition, and means directly responsive to a movement of said member along said first or second path tending to constrain the movement of said member along said third path.

15. Reversible motor control means comprising electrical switching means, an oscillatory memher for actuating said switching means, means for controlling said oscillatory member including a first element deflecting in accordance with the value ot'a condition and a second element actuated by said member and cooperating wth the the path of travel of the latter.

first-mentioned element.

16. 'I'he combination of claim 15 in which said elements are adapted for periodic engagement and are formed with engaging surfaces configured to selectively position one of said elements on each engagement, and means linking the lastmentioned element and the member 17. In apparatus of the class described the v combination of two switch-operating members,

a pendulum whose position with respect to a neutral position issubject to change by a condition to be controlled by said apparatus, a rockable and bodily displaceable sector plate adapted to actuate one or the other or neither of said members depending on its position in the plane of its swing prior to its being bodily displaced, and

means under the control of the pendulum for ad.- Justing the position of said plate in said plane, said sector plate having side notchesone at each radial side for establishing operative connection to determine between the plate andsaid switch-operating members.

18. In apparatus of the class described, the

combination oi two switch-operating members, a

pendulum whose position with respect to a neusaid plate, a finger extending across the plane of swing 0! said pendulum and carried by one of the arms oi. said lever, and means actuable by said plate (or adjusting the position of said finger with respect to the fulcrum point of said lever, said pendulum being adapted to arrest the upward movement oi said finger at one or the other oi two diflerent levels; 1

19. In apparatus of the class described, a pendulum whose pomtion with respect to a neutral position is subject to change by a condition to be assasss adapted to be actuated by said, plate for adjusting the position of said finger lengthwise of said arm, and circuit-controlling means adapted to be operated by said plate ii the latter actuates the finger adjusting means, said pendulum being adapted to arrest the upward movement of said finger.

20. In the combination specifiedin claim 19, means operated by said constantly rotating means for controlling the effective circuit-control period oi the circuit-controlling means. 7 21. In apparatus of the class described, a pen- "dulum whose position with respect to a neutral position is subject to change by a condition to be controlled by the apparatus, vertically reciprocable finger extending across the plane of swing of the pendulum and adapted to be arrested in its upward movement by the pendulum at either of two levels, a laterally extending arm on which the finger is laterally adjustable, means including a T-shape lever for adjusting the position oi the finger on said arm, and means for adjusting the controlled by the apparatus, a sector plate and means including a bell crank lever for rocking the plate, constantly rotating means for raising and lowering said plate and for rocking said lever, a laterally extending arm carried by said lever, a finger extending across the plane of swing of ,position of said lever comprising a vertically reciprocable: sector plate whose angular position may be adjusted with respect to the fulcrum oi.

said lever, said angular position determining whether or not the lever will be adjusted.

22. In the combination specified in claim 21, circuit-controlling means adapted to be actuated by said plate it the angular position or the latter said pendulum and carried by said arm, means is such as to cause said lever to be adjusted.

JOHN A. CALDWELL. 

